Base-facilitated production of hydrogen from carbonaceous matter

ABSTRACT

A base-facilitated process for producing hydrogen. Hydrogen is produced from a reaction of carbonaceous matter with a base and water, preferably through the formation of a bicarbonate or carbonate by-product. The base-facilitated hydrogen-producing reactions are thermodynamically more spontaneous and are able to produce hydrogen gas at less extreme reaction conditions than conventional reformation or gasification reactions of carbonaceous matter. In another embodiment, the instant reactions permit the production of hydrogen from carbonaceous matter without the production of carbon dioxide or carbon monoxide. In a preferred embodiment, the carbonaceous matter is coal or a derivative thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.10/763,616, entitled “Base-Facilitated Reformation Reactions of OrganicSubstances”, filed Jan. 23, 2004 now U.S. Pat. No. 7,481,992, andpublished as U.S. Pat. Appl. Pub. No. US2004/0156777 A1, the disclosureof which is herein incorporated by reference.

FIELD OF INVENTION

This invention relates to processes for producing hydrogen gas. Moreparticularly, this invention relates to the production of hydrogen gasfrom carbonaceous matter. Most particularly, the instant inventionrelates to the production of hydrogen gas through reactions ofcarbonaceous matter under alkaline conditions.

BACKGROUND OF THE INVENTION

Modern societies are critically dependent on energy derived from fossilfuels to maintain their standard of living. As more societies modernizeand existing modern societies expand, the consumption of fossil fuelscontinues to increase and the growing dependence worldwide on the use offossil fuels is leading to a number of problems. First, fossil fuels area finite resource and concern is growing that fossil fuels will becomefully depleted in the foreseeable future. Scarcity raises thepossibility that escalating costs could destabilize economies as well asthe likelihood that nations will go to war over the remaining reserves.Second, fossil fuels are highly polluting. The greater combustion offossil fuels has prompted recognition of global warming and the dangersit poses to the stability of the earth's ecosystem. In addition togreenhouse gases, the combustion of fossil fuels produces soot and otherpollutants that are injurious to humans and animals. In order to preventthe increasingly deleterious effects of fossil fuels, new energy sourcesare needed.

The desired attributes of a new fuel or energy source include low cost,plentiful supply, renewability, safety, and environmental compatibility.Hydrogen is currently a promising prospect for providing theseattributes and offers the potential to greatly reduce our dependence onconventional fossil fuels. Hydrogen is the most ubiquitous element inthe universe and, if its potential can be realized, offers aninexhaustible fuel source to meet the increasing energy demands of theworld. Hydrogen is available from a variety of sources including coal,natural gas, hydrocarbons in general, organic materials, inorganichydrides and water. These sources are geographically well distributedaround the world and accessible to most of the world's populationwithout the need to import. In addition to being plentiful and widelyavailable, hydrogen is also a clean fuel source. Combustion of hydrogenproduces water as a by-product. Utilization of hydrogen as a fuel sourcethus avoids the unwanted generation of the carbon and nitrogen basedgreenhouse gases that are responsible for global warming as well as theunwanted production of soot and other carbon based pollutants inindustrial manufacturing.

The realization of hydrogen as a ubiquitous source of energy ultimatelydepends on its economic feasibility. Economically viable methods forproducing hydrogen as well as efficient means for storing, transferring,and consuming hydrogen, are needed. Chemical and electrochemical methodshave been proposed for the production of hydrogen. The most readilyavailable chemical feedstocks for hydrogen are organic compounds,primarily hydrocarbons and oxygenated hydrocarbons. Common methods forobtaining hydrogen from hydrocarbons and oxygenated hydrocarbons aredehydrogenation reactions and oxidation reactions.

Steam reformation and the electrochemical generation of hydrogen fromwater through electrolysis are two common strategies currently used forproducing hydrogen. Both strategies, however, suffer from drawbacks thatlimit their practical application and/or cost effectiveness. Steamreformation reactions are endothermic at room temperature and generallyrequire temperatures of several hundred degrees to achieve acceptablereaction rates. These temperatures are costly to provide, impose specialrequirements on the materials used to construct the reactors, and limitthe range of applications. Steam reformation reactions also occur in thegas phase, which means that hydrogen must be recovered from a mixture ofgases through a separation process that adds cost and complexity to thereformation process. Steam reformation also leads to the production ofthe undesirable greenhouse gases CO₂ and/or CO as by-products. Waterelectrolysis has not been widely used in practice because highexpenditures of electrical energy are required to effect waterelectrolysis. The water electrolysis reaction requires a high minimumvoltage to initiate and an even higher voltage to achieve practicalrates of hydrogen production. The high voltage leads to high electricalenergy costs for the water electrolysis reaction and has inhibited itswidespread use.

In U.S. Pat. No. 6,607,707 (the '707 patent), the disclosure of which isincorporated by reference herein, the instant inventors considered theproduction of hydrogen from hydrocarbons and oxygenated hydrocarbonsthrough reactions of hydrocarbons and oxygenated hydrocarbons with abase. Using a thermodynamic analysis, the instant inventors determinedthat reactions of many hydrocarbons and oxygenated hydrocarbons reactspontaneously with a base or basic aqueous solution to form hydrogen gasat particular reaction conditions, while the same hydrocarbons andoxygenated hydrocarbons react non-spontaneously in conventional steamreformation processes at the same reaction conditions. Inclusion of abase was thus shown to facilitate the formation of hydrogen from manyhydrocarbons and oxygenated hydrocarbons and enabled the production ofhydrogen at less extreme conditions than those normally encountered insteam reformation reactions, thereby improving the cost effectiveness ofproducing hydrogen gas. In many reactions, the processes of the '707patent led to the formation of hydrogen gas from a liquid phase reactionmixture, in some cases at room temperature, where hydrogen was the onlygaseous product and thus was readily recoverable without the need for agas phase separation step. The reactions of the '707 patent furtheroperate through the formation of carbonate ion or bicarbonate ion andavoid the production of the greenhouse gases CO and CO₂. Inclusion of abase creates a new reaction pathway for the formation of hydrogen gaswith thermodynamic benefits that allow for the production of hydrogengas at lower temperatures than are needed for corresponding steamreformation processes.

In co-pending U.S. patent application Ser. No. 10/321,935 (the ″935application), published as U.S. Pat. Appl. Pub. No. 2003/0089620, thedisclosure of which is incorporated by reference herein, the instantinventors considered electrochemical methods to promote the productionof hydrogen from organic substances in the presence of water (or acidicsolution) and/or a base. They showed that electrochemical reactions oforganic substances with water to produce hydrogen require lowerelectrochemical cell voltages than water electrolysis. They also showedthat electrochemical reactions of organic substances in the presence ofan acid or base require low electrochemical cell voltages at roomtemperature.

In co-pending U.S. patent application Ser. No. 10/636,093 (the '093application), published as U.S. Pat. Appl. Pub. No. 2004/0028603, thedisclosure of which is incorporated by reference herein, the instantinventors recognized that the realization of the beneficial propertiesof the reactions described in the '707 patent and the co-pending '935application requires a system level consideration of the costs andoverall efficiency of the reactions. In addition to energy inputs andraw materials, consideration of the disposal or utilization ofby-products must be made. Of particular importance is consideration ofthe dispensation of the carbonate and bicarbonate ion products of thedisclosed hydrogen producing reactions. In the co-pending '093application, the instant inventors describe strategies for the recyclingof the carbonate and bicarbonate ions. A carbonate recycle process wasdescribed that includes a first step in which carbonate ion is reactedwith a metal hydroxide to form a soluble metal hydroxide and a weaklysoluble or insoluble carbonate salt. The soluble metal hydroxide may bereturned to the hydrogen producing reaction as a base reactant forfurther production of hydrogen. In a second step, the carbonate salt isthermally decomposed to produce a metal oxide and carbon dioxide. In athird step, the metal oxide is reacted with water to reform the metalhydroxide used in the first step. The carbonate recycle process is thussustainable with respect to the metal hydroxide and the overall hydrogenproducing process is sustainable with respect to the base through thecarbonate recycling process of the '093 application. Bicarbonateby-products of hydrogen producing reactions of organic substances withbases can be similarly recycled according to the '093 application byfirst converting a bicarbonate by-product to a carbonate and thenrecycling the carbonate.

In co-pending U.S. patent application Ser. No. 10/763,616 (the '616application), published as U.S. Pat. Appl. Pub. No. 2004/0156777, thedisclosure of which is incorporated by reference herein, the instantinventors described an extension of the base-facilitated production ofhydrogen from organic substances to a wider range of starting materials.Of particular importance in the ″616 was the production of hydrogen frompetroleum-related or petroleum-derived starting materials such as longchain hydrocarbons; fuels such as gasoline, kerosene, diesel, petroleumdistillates and components thereof; and mixtures of organic substances.

The hydrogen producing reactions of the '707 patent and the '935 and'616 applications provide for an efficient, environmentally friendlymethod for generating the hydrogen needed for the advancement of ahydrogen based economy. There is a need to further extend the range ofapplicability of the hydrogen producing reactions beyond what wasdescribed in the earlier patents and co-pending applications. Ofparticular interest is consideration of the range of starting materialsthat may be used in the reactions and the suitability of commonlyavailable organic substances for use as reactants. Also of interest isthe range of viable reaction conditions that are conducive to theformation of hydrogen gas and optimization of reaction conditions withrespect to trade-offs that may be present between reaction efficiency,reaction rate and process cost.

SUMMARY OF THE INVENTION

The instant invention provides a process for producing hydrogen gas fromchemical or electrochemical reactions of carbonaceous matter thereofwith bases in which carbonate and/or bicarbonate ion is produced as aby-product. The instant process optionally includes a carbonate ionrecycle process in which the carbonate ion by-product is transformed toa base that can subsequently be further reacted with an organicsubstance, mixture thereof or carbonaceous matter to produce hydrogengas.

The instant base-facilitated reformation reactions improve thethermodynamic spontaneity of producing hydrogen gas from carbonaceousmatter relative to the production of hydrogen gas through theconventional reformation of the carbonaceous matter. In one embodiment,the greater thermodynamic spontaneity permits the production of hydrogengas through the instant base-facilitated reactions of carbonaceousmatter at temperatures that are lower than those needed to producehydrogen gas from the carbonaceous matter in a conventional reformationreaction. In another embodiment, the greater thermodynamic spontaneitypermits the production of hydrogen gas from carbonaceous matter at afaster rate at a particular temperature in a base-facilitated reactionthan in a conventional reformation reaction of the carbonaceous matterat the particular temperature.

In a preferred embodiment, hydrogen is produced from reactions of coalwith a base and water in a chemical or electrochemical reaction. Coal iscarbonaceous matter that contains carbon, hydrogen, oxygen and otherelements in varying proportions. The instant base-facilitated reactionspermit the production of hydrogen from coal at lower temperatures orfaster rates relative to conventional steam reforming or gasificationreactions of coal. The reactions of the instant invention further permitthe production of hydrogen from coal without the co-production ofgreenhouse gases such as carbon dioxide and carbon monoxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Variation of hydrogen gas pressure as a function of reactiontime in a base-facilitated reaction of carbon at 210° C. and 220° C.

FIG. 2. Variation of hydrogen gas pressure as a function of reactiontime in a base-facilitated reaction of coal at 280° C.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The instant invention is concerned with an extension of the chemical andelectrochemical hydrogen producing reactions described in U.S. Pat. No.6,607,707 (the '707 patent), U.S. patent application Ser. No. 10/321,935(the '935 application), and U.S. patent application Ser. No. 10/763,616(the '616 application), the disclosures of which are incorporated byreference herein. The instant invention in particular provides for theproduction of hydrogen from carbonaceous matter. In a preferredembodiment, hydrogen is produced from coal in a base-facilitatedreformation reaction that proceeds through a carbonate ion or abicarbonate ion by-product. In another preferred embodiment, hydrogen isproduced from coal in a reaction that does not produce greenhouse gasesas a by-product.

The hydrogen producing reactions of the instant invention include thereaction of carbonaceous matter with a base. As used herein,carbonaceous matter refers generally to naturally occurringcarbon-containing materials and substances. In a preferred embodiment,the carbonaceous matter is coal. Coal is a natural solid that isnormally brown to black in color. Coal is the product of physical andchemical alterations of vegetation. Original accumulations of vegetation(e.g. woody plants) in a swamp or moist environment led to the formationof peat. Peat is converted to coal upon burial through the action ofgeologic processes that involve increases in pressure and temperaturethat act to compress and harden the material and to alter the chemicalcomposition. The geologic processes responsible for the formation ofcoal lead to an increase in the carbon content and a decrease in theoxygen and hydrogen content of the material relative to the plant matterfrom which the coal formation process is initiated. Coal can thus beviewed as being rich in carbon relative to plant matter, biomass andother renewable organics. Coal typically includes carbon along withvarious organic and inorganic compounds or elements.

Various coals may be used as starting materials in the instanthydrogen-producing reactions, including anthracitic, bituminous,sub-bituminous, and lignitic coals. The primary constituents of coal arecarbon (C), hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S). Thedifferent ranks of coal differ in the relative proportions of theseconstituents and these differences lead to differences in the heatingvalue of coal. Generally speaking, the higher the rank is, the greateris the carbon content and the greater is the heating value of coal. Thecarbon content of different ranks of coal, on average, typicallydecreases in the following order:

-   -   Anthracite>Bituminous>Sub-Bituminous>Lignite

A compositional analysis of representative samples of different ranks ofcoal is provided in Table 1 hereinbelow. The compositions are selectedexamples taken from a database maintained

TABLE 1 Ultimate Analysis of Selected Samples of Coal (Wt. %) SampleRank Location H C N O S C/H D205172 Lignite AR 7.00 31.10 0.60 46.100.70 4.44 D173470 Lignite CO 6.70 36.40 0.60 42.30 0.30 5.43 D189152Sub-bituminous MT 6.20 37.10 0.80 45.90 0.70 5.98 W236221 Lignite TX5.52 44.03 0.79 29.18 1.24 7.97 W233983 Bituminous AL 4.84 44.12 0.8631.76 0.42 9.12 D178913 Sub-bituminous WA 5.70 48.10 0.80 30.50 0.408.43 W202688 Bituminous OH 4.70 54.90 1.10 23.30 0.70 11.68 D182628Bituminous MO 5.30 57.40 0.80 14.70 6.10 10.83 W189011 Bituminous MD3.70 62.50 1.40 4.60 2.10 16.89 W218960 Bituminous GA 3.86 65.54 1.234.55 0.87 16.98 D172594 Bituminous MI 5.80 70.00 1.40 19.00 1.20 12.07W206444 Bituminous PA 5.50 76.70 1.40 9.00 1.00 13.94 W184939 AnthracitePA 2.50 85.60 0.80 3.70 0.60 34.24 (Locations: AR = Arkansas, CO =Colorado, MT = Montana, TX = Texas, AL = Alabama, WA = Washington, OH =Ohio, MO = Missouri, MD = Maryland, GA = Georgia, MI = Michigan, PA =Pennsylvania)by the United States Geological Survey and are based on an ultimateanalysis. The table includes the amount, in weight percent, of theprimary elemental constituents of natural coal samples as well as theweight percent ratio of carbon to hydrogen (C/H). The samples includedin Table 1 are representative examples of coals suitable for use in theinstant invention.

The plant and natural organic matter from which coal is derived (e.g.biomass) is comprised of organic compounds. Carbohydrates are primarycomponents of biomass. The most abundant components of biomass aremonosaccharides such as glucose, which has a chemical formula C₆H₁₂O₆.In terms of elemental weight percent, glucose is made up of 40.00%carbon, 6.67% hydrogen and 53.33% oxygen. As can be seen from Table 1,the vast majority of coals have a higher proportion of carbon, a lowerproportion of hydrogen and a lower proportion of oxygen than biomass.The differences in the proportions of the elements reflect the naturalevolution of the composition of coal.

In the instant invention hydrogen is produced from a reaction of thecarbon contained in coal and the amount of hydrogen formed varies withthe carbon content of the coal. The instant invention may further permitthe liberation of hydrogen contained in coal as hydrogen gas. In oneembodiment, hydrogen is formed from coal having a weight percent ofcarbon between of 45% and 95%. In one embodiment, hydrogen is formedfrom coal having a weight percent of carbon between 50% and 90%. Inanother embodiment, hydrogen is formed from coal having a weight percentof carbon between 55% and 85%. In still another embodiment, hydrogen isformed from coal having a weight percent of carbon between 60% and 75%.In other embodiments, the coal or carbonaceous matter includes amorphouscarbon. Other carbonaceous materials within the scope of the instantinvention include peat, coke, and coal tar as well as other derivativesand by-products of coal.

In further embodiments of the instant invention, the carbonaceous matteris characterized by a high ratio of the weight percent of carbon to theweight percent of hydrogen. The ratio of the weight percent of carbon tothe weight percent of hydrogen may be referred to herein as thecarbon/hydrogen weight percent ratio. In one embodiment, thecarbon/hydrogen weight percent ratio is greater than 6. In anotherembodiment, the carbon/hydrogen weight percent ratio is greater than 8.In still another embodiment, the carbon/hydrogen weight percent ratio isgreater than 10. In still another embodiment, the carbon/hydrogen weightpercent ratio is greater than 12. In another embodiment, thecarbon/hydrogen weight percent ratio is greater than 16.

In the instant invention, carbonaceous matter is utilized as a feedstockor starting material in a base-facilitated hydrogen-producing reaction.As discussed in the '707 patent, the '935 application and '616application, reactions of organic substances with a base permit theproduction of hydrogen gas through the formation of carbonate ion and/orbicarbonate ion by-products. Inclusion of a base as a reactant in theproduction of hydrogen from organic substances thus provides analternative reaction pathway relative to conventional reformationreactions of organic substances, which proceed through a reactionpathway that leads to the production of CO₂ from a reaction of anorganic substance with water.

In the instant invention, base-facilitated reactions of carbonaceousmatter are demonstrated. The instant base-facilitated reactions lead tothe production of hydrogen from carbonaceous matter. More particularly,the instant reactions permit formation of hydrogen from a reaction ofthe carbon contained in carbonaceous matter. The instant reactionsprovide an alternative reaction pathway of carbonaceous matter thatleads to a more spontaneous (or less non-spontaneous) reaction at aparticular set of reaction conditions relative to a conventionalreformation reaction of the carbonaceous matter. The instant inventionmay further permit the liberation of hydrogen contained in carbonaceousmatter as hydrogen gas.

Currently, reformation of coal occurs through a set of reactions thatbegins with reaction (1) below, where carbon is the principle reactingcomponent of coal and competing side reactions are neglected for thepurposes of this discussion.C_((s))+H₂O_((g))⇄CO_((g))+H_(2(g))  (1)In this reaction, C_((s)) designates the carbon contained in coal. Theproduct mixture of carbon monoxide (CO) and H₂ gases is known as syngasand can be further reacted to produce other hydrogenated organic fuelssuch as methanol or ethanol. Alternatively, the carbon monoxide ofsyngas can be reacted via the water-gas shift reaction (2) to produceadditional hydrogen:CO_((g))+H₂O_((g))⇄CO_(2(g))+H_(2(g))  (2)By combining reactions (1) and (2), a net coal reaction can be writtenas shown in reaction (3) below:C_((s))+2H₂O_((g))⇄CO_(2(g))+2H_(2(g))  (3)

A thermodynamic analysis can be used to predict the facility of the coalreaction (3). Specifically of interest are the Gibbs free energy andenthalpy change of reaction. The Gibbs free energy is an indicator ofthe thermodynamic spontaneity of a chemical reaction. Spontaneousreactions have negative values for the Gibbs free energy, whilenon-spontaneous reactions have positive values for the Gibbs freeenergy. A spontaneous reaction is a reaction that proceeds without theadditional input of energy at a particular set of reaction conditions.Reaction conditions such as reaction temperature, reaction pressure,concentration etc. may influence the value of the Gibbs free energy. Areaction that is non-spontaneous at one set of conditions may becomespontaneous at another set of conditions. The magnitude of the Gibbsfree energy is an indicator of the degree of spontaneity of a reaction.The more negative (or less positive) the Gibbs free energy is, the morespontaneous is the reaction.

The enthalpy change of a reaction indicates whether a reaction isendothermic or exothermic. Endothermic reactions are reactions thatrequire an input of heat to perform, while exothermic reactions requireno input of heat to initiate and instead release energy. The costs orprocess modifications associated with providing heat to endothermicreactions are generally undesirable, so there is a general preferencefor exothermic reactions.

A thermodynamic analysis of reaction (1) above indicates that ΔG⁰_(rxn)=21.9 kcal/mol and ΔH⁰ _(rxn)=31.5 kcal/mol, where ΔG⁰ _(rxn) andΔH⁰ _(rxn) are the Gibbs energy and enthalpy of reaction at standardconditions (25° C., 1 atm. and unit activity of reactants and products),respectively. The thermodynamic parameters indicate that reaction (1) isboth non-spontaneous and endothermic at standard conditions andtherefore that reaction (1) must be at more extreme reaction conditions.In practice, the results indicate that reaction (1) requires elevatedreaction temperatures in order to become spontaneous and to proceed at apractically useful rate.

A corresponding analysis of reaction (3) shows that ΔG⁰ _(rxn)=15.1kcal/mol and ΔH⁰ _(rxn)=21.7 kcal/mol. As is the case for reaction (1),reaction (3) is both non-spontaneous and endothermic at standardconditions and thus requires elevated reaction temperatures to producehydrogen at practical rates.

In the instant invention, hydrogen is produced from coal in abase-facilitated reaction that avoids the need to proceed via theformation of CO or CO₂. Instead, hydrogen is produced from the carbon incoal via a carbonate and/or bicarbonate by-product compound as shown inthe base-facilitated reactions (4) and (5):C_((s))+2NaOH_((s))+H₂O_((g))⇄2H_(2(g))+Na₂CO_(3(s))  (4)C_((s))+NaOH_((s))+2H₂O_((g))⇄2H_(2(g))+NaHCO_(3(s))  (5)In these reactions, sodium hydroxide (NaOH) is a base, sodium carbonate(Na₂CO₃) is a carbonate compound by-product and sodium bicarbonate(NaHCO₃) is a bicarbonate compound by-product. In a given reaction ofcoal with a base, either or both of a carbonate or bicarbonateby-product may be formed with the relative proportion of the carbonateand bicarbonate by-products being determined by the ratio of base to thecarbon in the coal.

The thermodynamic parameters of reaction (4) are ΔG⁰ _(rxn)=−13.7kcal/mol and ΔH⁰ _(rxn)=−9.1 kcal/mol and the thermodynamic parametersof reaction (5) are ΔG⁰ _(rxn)=−3.5 kcal/mol and ΔH⁰ _(rxn)=−10.0kcal/mol. Both base-facilitated reactions are spontaneous and exothermicat standard conditions. In practice, both reactions are expected toproduce hydrogen at appreciable rates at much less extreme conditionsthan the coal reaction (3).

The base-facilitated reactions (4) and (5) demonstrate the beneficialeffect of a base on the thermodynamic spontaneity of the production ofhydrogen from coal. The thermodynamic spontaneity of reactions (4) and(5) at standard conditions indicates that hydrogen can be producedspontaneously at standard conditions from coal through the instantbase-facilitated reactions, whereas the spontaneous production ofhydrogen from coal via the reaction (3) is not possible at standardconditions.

The rate of production of hydrogen gas is another importantconsideration of interest to the instant inventors. It is generallypreferred to produce hydrogen gas at the fastest rate possible. Inaddition to influencing the spontaneity of a reaction, it is generallythe case that once a reaction is spontaneous, an increase in temperatureincreases the rate of a reaction. In the instant base-facilitatedhydrogen-producing reactions (4) and (5), the rate of hydrogenproduction increases as the temperature is increased above the standardstate temperature.

The greater spontaneity of hydrogen production afforded by the instantbase-facilitated hydrogen-producing reactions indicates that at aparticular reaction temperature, the rate of production of hydrogen ishigher for a base-facilitated reaction according to the instantinvention than for reaction (3). At temperatures at whichbase-facilitated reaction (4) or (5) of coal is spontaneous and reaction(3) is non-spontaneous, the rate of production of hydrogen is greaterfor the base-facilitated reaction than for the reaction. Above a certaintemperature, reaction (3) and the instant base-facilitated reactions (4)or (5) of coal are all spontaneous. Even at temperatures at whichreaction (3) and the base-facilitated reactions are all spontaneous, itremains the case that the instant base-facilitated reactions are morespontaneous than reaction (3). At a common temperature at which reaction(3) and the instant base-facilitated reactions of coal are allspontaneous, the rate of production of hydrogen is greater for thebase-facilitated reactions than for reaction (3). The beneficial effectsof including a base in the instant reaction thus include a greater rateof production of hydrogen relative to reaction (3) at a particularreaction temperature due to the greater spontaneity of the instantbase-facilitated reactions.

The advantages of the instant base-facilitated reactions are alsomanifested over a wide range of conditions of temperature, pressure,species concentration etc. The greater spontaneity of the instantbase-facilitated hydrogen production reactions leads to faster rates ofproduction of hydrogen at common reaction conditions for the instantreactions relative to reaction (3), even at temperatures or otherconditions for which reaction (3) is also spontaneous. Also, if aparticular rate of formation of hydrogen is required, that rate can beachieved at less extreme (e.g. at lower temperature) through the instantbase-facilitated reactions than through reaction (3).

The thermodynamic spontaneity analysis indicates generally thatproduction of hydrogen from coal becomes increasingly more spontaneousas the amount of base in the reaction increases. Reaction (3) has nobase present and is less spontaneous than base-facilitated reaction (5)having a low concentration of base present which is less spontaneousthan base-facilitated reaction (4) having a high concentration of basepresent. As a result, the instant base-facilitated reformation reactionsbecome spontaneous at less extreme reaction conditions (e.g. lowerreaction temperatures) than reaction (3) and further produce hydrogen atfaster rates at common conditions. The instant base-facilitatedreactions also permit the production of hydrogen while avoiding thesimultaneous production of the greenhouse gases CO and CO₂.

EXAMPLE 1

In this example, the production of hydrogen from carbon is described.0.3 g of carbon black and 2.0 g of solid sodium hydroxide wereintimately mixed and placed into a stainless steel cylinder reactorhaving a volume of ˜40 mL. The sodium hydroxide included about 5% byweight of water. The carbon black and sodium hydroxide occupied about25% of the volume of the reactor. Electrical coils were wrapped aroundthe reactor for heating and the temperature was controlled with athermocouple attached to the bottom of the reactor. The reactor wassealed and then flushed with helium to remove oxygen from the reactor.In the flushing process, the cylinder was first evacuated with a vacuumpump and then charged with flowing helium until the pressure reachedabout atmospheric pressure. The process was performed three times.

At the end of the third charge with helium, the helium was left in thereactor and the pressure at room temperature was measured to be about 17psi. The reactor was wrapped with insulation, raised to the desiredreaction temperature and connected to a data acquisition system thatrecorded the pressure change in the reactor as a function of time. Datawere taken at several different temperatures. At each temperature,hydrogen was generated by the instant reaction and the experiment washalted when sufficient time had elapsed to create a pressure of ˜50 psiin the reactor. Upon reaching this pressure, the process was stopped andthe reactor was allowed to cool down to room temperature. When thereactor returned to room temperature, a sample of the gas was taken andanalyzed with a gas chromatograph to confirm the presence of hydrogengas.

The results obtained at 210° C. and 220° C. are shown in FIG. 1 herein.The graph shows the change in the pressure of the reactor due to theproduction of hydrogen gas from carbon as a function of time up to ˜1.75hr. At both temperatures, hydrogen is produced at nearly linear rate.The data at 220° C. indicate a faster rate of production of hydrogenthan the data at 210° C., an observation of the general tendency for therate of a chemical reaction to increase with increasing temperature.

This example demonstrates the production of hydrogen from a reaction ofcarbon with sodium hydroxide and water.

EXAMPLE 2

In this example, the production of hydrogen from coal is described. Thecoal sample used in this experiment was received from Basic Services, acoal company with a location in Virginia. The sample was excavated outof a part of the raven coal bed located in St. Paul, Va. (Wise County).A chemical analysis of the specific sample used in this experiment wasnot obtained, but the USGS database mentioned hereinabove provides thefollowing information for three samples extracted from the raven coalbed located in St. Paul, Va.:

TABLE 2 Ultimate Analysis of Selected Samples of Coal extracted from theRaven Coal Bed (Wt. %) Sample Rank Location H C N O S C/H W203384Bituminous Virginia 5.10 73.70 1.40 8.00 0.90 14.45 W215446 BituminousVirginia 4.84 72.05 1.52 6.50 1.10 14.89 W193664 Bituminous Virginia4.70 70.90 1.40 6.80 1.20 15.09

1.0 g of the coal sample and 7.0 g of solid sodium hydroxide wereintimately mixed and placed into a stainless steel cylinder reactorhaving a volume of ˜40 mL. The sodium hydroxide included about 5% byweight of water. The coal and sodium hydroxide occupied about 25% of thevolume of the reactor. Electrical coils were wrapped around the reactorfor heating and the temperature was controlled with a thermocoupleattached to the bottom of the reactor. The reactor was sealed and thenflushed with helium to remove oxygen from the reactor. In the flushingprocess, the cylinder was first evacuated with a vacuum pump and thencharged with flowing helium until the pressure reached about atmosphericpressure. The process was performed three times.

At the end of the third charge with helium, the helium was left in thereactor and the pressure at room temperature was measured to be about 17psi. The reactor was wrapped with insulation, raised to the desiredreaction temperature and connected to a data acquisition system thatrecorded the pressure change in the reactor as a function of time. Datawere taken at several different temperatures. At each temperature,hydrogen was generated by the instant reaction and the experiment washalted when sufficient time had elapsed to create a pressure of ˜50 psiin the reactor. Upon reaching this pressure, the process was stopped andthe reactor was allowed to cool down to room temperature. When thereactor returned to room temperature, a sample of the gas was taken andanalyzed with a gas chromatograph to confirm the presence of hydrogengas.

The results obtained at 280° C. are shown in FIG. 2 herein. The graphshows the change in the pressure of the reactor due to the production ofhydrogen gas from coal as a function of time up to ˜3.4 hr. The dataindicate that hydrogen is produced steadily over time.

This example demonstrates the production of hydrogen from a reaction ofcoal with sodium hydroxide and water and generally shows the productionof hydrogen from carbon contained within carbonaceous matter.

In the foregoing examples, water was present as an adsorbate in thesodium hydroxide. The instant invention further contemplates use of anaqueous base or reaction of carbonaceous matter with a solid phase basein the presence of liquid water or water vapor.

Metal hydroxides are the preferred bases in the instant reactions.Representative metal hydroxides include alkali metal hydroxides (e.g.NaOH, KOH etc.) alkaline earth metal hydroxides (e.g. Ca(OH)₂, Mg(OH)₂,etc.), transition metal hydroxides, post-transition metal hydroxides andrare earth hydroxides. Non-metal hydroxides such as ammonium hydroxidemay also be used. At standard state conditions, most hydroxide compoundsare solids and the solid phase is one preferred form of introducingmetal hydroxide bases in the instant reactions. When using a solid phasebase, the base can be intimately mixed with a carbonaceous materialthrough, for example, grinding. Alternatively, the base can be appliedas a surface layer onto a carbonaceous material. Aqueous solutions areanother preferred solution form of hydroxide compounds. Still otherpreferred forms of providing a base as a reactant in the instantreactions include suspensions of solid phase bases and molten phasebases, where molten phase bases may be formed upon heating a solid phasebase to a reaction temperature desired for a particularhydrogen-producing reaction according to the instant invention.

In a further embodiment of the instant invention, the instantbase-facilitated reactions are conducted electrochemically to producehydrogen from carbonaceous matter. As described in the parent '935application, inclusion of a base in a reformation reaction reduces theelectrochemical potential (voltage) required to effect the production ofhydrogen from an organic substance relative to the production ofhydrogen from the corresponding conventional electrochemical reformationreaction. The instant invention further includes electrochemicalreactions in accordance with the parent '935 application as applied tothe production of hydrogen from carbonaceous matter. In theseembodiments, carbonaceous matter is placed in an electrochemical cellhaving an anode and a cathode and a voltage is applied between the anodeand cathode to effect the electrolytic production of hydrogen from thecarbonaceous matter in an electrochemical reaction in accordance withthe '935 application. In a preferred embodiment, an aqueous or otherelectrolyte is included along with the carbonaceous matter and base inthe electrochemical cell.

In yet another embodiment of the instant invention, the instantbase-facilitated reactions are conducted in combination with thecarbonate or bicarbonate recovery reactions discussed in the co-pendingparent '093 application. The carbonate or bicarbonate recovery reactionsare intended to improve the overall efficiency of the production ofhydrogen from carbonaceous matter. As indicated hereinabove, in theembodiments of the instant base-facilitated reaction, carbonate orbicarbonate compounds are produced as a by-product of the reaction. Acarbonate or bicarbonate compound is a side product that needs to besold as a commodity, utilized, discarded or otherwise dispensed with. Inorder to improve the efficiency of hydrogen production, it is desirableto recycle or otherwise utilize the carbonate or bicarbonate compoundby-product.

The '093 application discusses recovery reactions that may be used torecycle carbonate or bicarbonate by-products. Various reactions arediscussed depending on the form of the carbonate or bicarbonateby-product formed in the instant base-facilitated reaction. As anexample, if a carbonate by-product is formed as a metal carbonateprecipitate, this precipitate can be collected and thermally decomposedto obtain a metal oxide. This metal oxide can subsequently be reactedwith water to form a metal hydroxide that can be returned as a basereactant to the instant base-facilitated reaction. As another example,if a carbonate by-product is formed as a metal carbonate that is solublein the reaction mixture, further reaction with a metal hydroxide mayoccur where the metal hydroxide is selected so that the carbonate saltof its metal has a low solubility (low K_(sp)) so that a metathesisreaction occurs to precipitate out a metal carbonate while leavingbehind a soluble metal hydroxide that can be used as a base reactant infurther runs of the instant base-facilitated reactions. Bicarbonateby-products may be similarly re-utilized. The method of producinghydrogen gas through the instant base-facilitated reformation reactionsmay thus optionally include additional steps directed at the recycling,conversion or re-utilization of carbonate or bicarbonate by-products inaccordance with the '093 application.

The foregoing discussion and description are not meant to be limitationsupon the practice of the present invention, but rather illustrativethereof. It is to be appreciated by persons of skill in the art thatnumerous equivalents of the illustrative embodiments disclosed hereinexist. It is the following claims, including all equivalents and obviousvariations thereof, in combination with the foregoing disclosure whichdefine the scope of the invention.

1. A process for producing hydrogen gas comprising the step of reactingcarbonaceous matter with a base to form said hydrogen gas, saidcarbonaceous matter comprising carbon, wherein the weight percent ofcarbon in said carbonaceous matter is between 45% and 95%; wherein saidreaction step includes an electrochemical reaction, said electrochemicalreaction occurring in an electrochemical cell into which saidcarbonaceous matter, said base and an electrolyte are placed to form anelectrochemical reaction system, said electrochemical cell including ananode and cathode in contact with said electrochemical system, saidelectrochemical reaction being initiated upon applying a voltage betweensaid anode and said cathode.
 2. The process of claim 1, wherein theweight percent of carbon in said carbonaceous matter is between 50% and90%.
 3. The process of claim 1, wherein the weight percent of carbon insaid carbonaceous matter is between 55% and 85% by weight.
 4. Theprocess of claim 1, wherein the weight percent of carbon in saidcarbonaceous matter is between 60% and 75%.
 5. The process of claim 1,wherein said carbonaceous matter further comprises hydrogen.
 6. Theprocess of claim 5, wherein the carbon/hydrogen weight percent ratio isgreater than
 6. 7. The process of claim 5, wherein the carbon/hydrogenweight percent ratio is greater than
 8. 8. The process of claim 5,wherein the carbon/hydrogen weight percent ratio is greater than
 10. 9.The process of claim 5, wherein the carbon/hydrogen weight percent ratiois greater than
 12. 10. The process of claim 5, wherein thecarbon/hydrogen weight percent ratio is greater than
 16. 11. The processof claim 5, wherein said carbonaceous matter further comprises oxygen.12. The process of claim 11, wherein said carbonaceous matter furthercomprises nitrogen.
 13. The process of claim 1, wherein saidcarbonaceous matter is coal.
 14. The process of claim 13, wherein therank of said coal is lignite.
 15. The process of claim 13, wherein therank of said coal is sub-bituminous.
 16. The process of claim 13,wherein the rank of said coal is bituminous.
 17. The process of claim13, wherein the rank of said coal is anthracite.
 18. The process ofclaim 1, wherein said carbonaceous matter is coke, coal tar or peat. 19.The process of claim 1, wherein said carbonaceous mater comprisesamorphous carbon.
 20. The process of claim 1, wherein said carbonaceousmatter undergoes said hydrogen-producing reaction in the solid phase.21. The process of claim 1, wherein said carbonaceous mailer and saidbase undergo said hydrogen-producing reaction in the presence of liquidwater or water vapor.
 22. The process of claim 1, wherein saidhydrogen-producing reaction does not form carbon dioxide or carbonmonoxide.
 23. The process of claim 1, wherein said base comprises ahydroxide compound.
 24. The process of claim 23, wherein said hydroxidecompound is a metal hydroxide compound.
 25. The process of claim 24,wherein said metal hydroxide compound is an alkali metal hydroxidecompound.
 26. The process of claim 1, wherein said hydrogen-producingreaction further forms a carbonate or bicarbonate compound.
 27. Theprocess of claim 26, further including the step of reacting saidcarbonate or bicarbonate compound with a metal hydroxide compound. 28.The process of claim 27, further including the step of thermallydecomposing said carbonate or bicarbonate precipitate, said thermaldecomposition step producing a metal oxide.
 29. The process of claim 1,wherein said base is a metal hydroxide.